The present invention relates to engine lubricants and the use of certain functionalized polymers for improved fuel economy in crankcase lubricants for internal combustion engines and other lubricating applications for transportation vehicles.
There are continuing efforts for improving fuel economy of internal combustion engines and in the vehicles which they propel. One way by which fuel economy can be improved is by reducing the internal friction within the engine itself. This may be accomplished by appropriate choice of lubricants to reduce friction and thus promote ease of movement of various engine parts, in addition to the numerous other benefits and properties provided by the lubricant. One way in which friction can be reduced is by employing base oils of relatively lower viscosity, and indeed there has been a trend in recent years to use of lower viscosity oils. However, one cannot simply reduce the viscosity of the lubricant without risking diminution of other benefits provided by the lubricant, such as protection against wear. Thus, for low viscosity oils, the formulation of the lubricant, and in particular the selection of additives incorporated within the base oil, is very important. A selection of additive or additives to reduce internal friction within an engine, regardless of the viscosity of the base oil, leading to improved fuel economy, will be highly desirable.
Numerous patents have appeared relating to additives for engine oils, seeking to provide various benefits. As an example, U.S. Pat. No. 6,124,249, Seebauer et al., Sep. 26, 2000, discloses viscosity improvers for lubricating oil compositions. It discloses a copolymer comprising units derived from (a) methacrylic acid esters containing from about 9 to about 25 carbon atoms in the ester group and (b) methacrylic acid esters containing from 7 to about 12 carbon atoms in the ester group, and optionally (c) at least one monomer which may be, among others, nitrogen-containing vinyl monomers. Examples are given of polymers prepared from 272.8 parts C12-15 methacrylate, 120 parts 2-ethylhexyl methacrylate, and 7.2 parts dimethylaminopropylmethacrylamide. These materials are described as viscosity improvers or viscosity index improvers, and they may also enhance dispersant properties of lubricants.
U.S. Patent Application 2004/0254080, Sivik et al., Dec. 16, 2004, discloses polymer compositions with α,β-unsaturated ester monomers and at least one unsaturated dicarboxylic acid anhydride or derivatives thereof, and optionally at least one non-monomeric amine with primary functionality, secondary functionality, or mixtures thereof.
The present invention solves the problem of providing a lubricant which imparts reduced frictional losses to an engine or other mechanical device by incorporating therein a selected polymer, along with one or more additional additives. The lubricant of the present invention may be used to lubricate engines operating on a variety of fuels, including gasoline, diesel, alcohols, mixtures thereof, and hydrogen.